[Devel] [PATCH RHEL7 COMMIT] ploop: Set up discard limits

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-957.1.3.vz7.93.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-957.1.3.vz7.83.17
------>
commit 5122dfa543f5b2034bde29950c7f25890e802201
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Wed Mar 6 14:22:49 2019 +0300

    ploop: Set up discard limits
    
    Logical neighbouring blocks usually are not physically
    neighbours, so we may issue discard only for a single
    block. Thus, we request block layer to split discard
    requests in (1 << (cluster_log + 9)) bytes bios.
    
    This is the basis. Later we may introduce some performance
    improvements for corner cases on top of this.
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    
    =====================
    Patchset description:
    
    ploop: Add online discard support for dio engine
    
    The first part of patchset is preparations to make code
    a bit readable.
    
    The second part adds online discard support for dio engine.
    DIO engine tracks entents, so discard code will use that
    for its needs.
    
    https://pmc.acronis.com/browse/VSTOR-19972
    
    Kirill Tkhai (12):
          ploop: introduce dio_may_fallocate() helper
          ploop: Export whole_block()
          ploop: Add cluster_size_in_bytes() helper
          ploop: Add cluster_size_in_sec() helper
          ploop: Add local variable into dio_submit()
          ploop: Add cluster_log local variable
          ploop: Add trim_extent_mappings_tail() helper
          ploop: Introduce local variable in ploop_start()
          ploop: Never merge discard requests
          ploop: Set up discard limits
          ploop: Introduce ploop_can_issue_discard() helper
          ploop: Online discard support for dio engine
---
 drivers/block/ploop/dev.c       |  6 +++---
 drivers/block/ploop/io_direct.c |  1 +
 drivers/block/ploop/io_kaio.c   |  5 +----
 include/linux/ploop/ploop.h     | 11 +++++++++++
 4 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/block/ploop/dev.c b/drivers/block/ploop/dev.c
index 9ac436201b1b..bf508a9b1bc8 100644
--- a/drivers/block/ploop/dev.c
+++ b/drivers/block/ploop/dev.c
@@ -4026,10 +4026,10 @@ static int ploop_start(struct ploop_device * plo, struct block_device *bdev)
 	blk_queue_merge_bvec(q, ploop_merge_bvec);
 	blk_queue_flush(q, REQ_FLUSH);
 
-	if (top_delta->io.ops->queue_settings)
-		top_delta->io.ops->queue_settings(&top_delta->io, q);
+	top_delta->io.ops->queue_settings(&top_delta->io, q);
+	/* REQ_WRITE_SAME is not supported */
+	blk_queue_max_write_same_sectors(q, 0);
 
-	blk_queue_max_discard_sectors(q, INT_MAX);
 	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 	queue_flag_clear_unlocked(QUEUE_FLAG_STANDBY, q);
 
diff --git a/drivers/block/ploop/io_direct.c b/drivers/block/ploop/io_direct.c
index b0d7095864fc..18563eaa4f1a 100644
--- a/drivers/block/ploop/io_direct.c
+++ b/drivers/block/ploop/io_direct.c
@@ -1776,6 +1776,7 @@ static int dio_congested(struct ploop_io * io, int bits)
 
 static void dio_queue_settings(struct ploop_io * io, struct request_queue * q)
 {
+	ploop_set_discard_limits(io->plo);
 	blk_queue_stack_limits(q, bdev_get_queue(io->files.bdev));
 }
 
diff --git a/drivers/block/ploop/io_kaio.c b/drivers/block/ploop/io_kaio.c
index f5d9936d4cd4..84da1cec5643 100644
--- a/drivers/block/ploop/io_kaio.c
+++ b/drivers/block/ploop/io_kaio.c
@@ -1078,10 +1078,7 @@ static void kaio_unplug(struct ploop_io * io)
 static void kaio_queue_settings(struct ploop_io * io, struct request_queue * q)
 {
 	blk_set_stacking_limits(&q->limits);
-	blk_queue_max_write_same_sectors(q, 0);
-
-	q->limits.discard_alignment = PAGE_SIZE;
-	q->limits.discard_granularity = PAGE_SIZE;
+	ploop_set_discard_limits(io->plo);
 }
 
 static void kaio_issue_flush(struct ploop_io * io, struct ploop_request *preq)
diff --git a/include/linux/ploop/ploop.h b/include/linux/ploop/ploop.h
index 71a55573bdf6..b209c9f096a8 100644
--- a/include/linux/ploop/ploop.h
+++ b/include/linux/ploop/ploop.h
@@ -853,6 +853,17 @@ static inline bool whole_block(struct ploop_device * plo, struct ploop_request *
 	return !(preq->req_sector & (cluster_size_in_sec(plo) - 1));
 }
 
+static inline void ploop_set_discard_limits(struct ploop_device *plo)
+{
+	struct request_queue *q = plo->queue;
+	/*
+	 * In PLOOP_FMT_PLOOP1 format, neighbouring virtual clusters
+	 * are not neighbours on backed device, so we expect block
+	 * subsystem splits discards in single-cluster requests.
+	 */
+	q->limits.discard_granularity = cluster_size_in_bytes(plo);
+	q->limits.max_discard_sectors = (1 << plo->cluster_log);
+}
 struct map_node;
 
 int ploop_fastmap(struct ploop_map * map, cluster_t block, iblock_t *result);